15 Sputtering 10

15 Sputtering 10 - Sputtering This lecture covers how...

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Many metals, particularly aluminum alloys, and barrier materials such as TiN or TiW are sputtered process has a high degree of control and is capable of depositing multi- element films. Sputtering This lecture covers how materials are deposited using physical vapor deposition (PVD)
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Process requirements Metallization processes must give Low resistance tracks Good ohmic contacts to silicon High current density in tracks Fast deposition rate Safe and robust techniques Good yield and cost No product degradation
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Starting point: Al evaporation Vacuum bell-jar Wafers on planetary holder Hot Al source Vacuum pumps Al evaporates when heated at low pressure Evaporation is cheap and simple but… Needs good vacuum -hot source Difficult to control composition of multi-element films Get shadow effects due to point source So we need something better!
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Small-geometry requirements 1 Good low R contact to Si 2 No damage to shallow junction 3 Uniform current density Contact to source or drain in MOS device
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Metallurgy of contacts Sinter Al film at 430 o C in hydrogen to make good ohmic contacts to n + or p + Si BUT… Si is slightly soluble in Al So diffusion down grain boundaries Al into Si AND Si into Al GET SPIKING! Al Si Spike
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Make an alloy of Al with ~2% Si - migration is stopped. BUT… If we try to evaporate the alloy, it dissociates and no silicon is deposited (it gets left behind) . SO…
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This note was uploaded on 05/11/2010 for the course EEE EEE-530 taught by Professor Kozicki during the Spring '10 term at ASU.

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15 Sputtering 10 - Sputtering This lecture covers how...

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